Platypus fur is extremely fine and even denser than that of polar bears and river otters, with up to 900 hairs covering each square millimetre of skin!

Platypus fur also has two layers - a woolly undercoat and longer, shiny guard hairs - which work together to trap a layer of air next to the skin, keeping most of the animal's body dry even when diving.

For the platypus to stay warm while in the water, its fur must remain completely clean and waterproof, and not be fouled by oil or other pollutants.

An important element in its behaviour is the grooming of its fur. Sometimes this occurs in the water, but more often it occurs on a particular log or rock.

In such conditions, hearing and eye-sight are of little use in detecting prey.

The platypus closes both its eyes and ears (which are located in a groove behind the eyes) and relies on its "sixth sense" - an electro-receptor system. This system is located in the bill and helps it detect the small flickers of electricity produced by the aquatic creatures that it feeds on.

The bill also contains various pressure sensors, which together with the electro-receptors, probably assist navigation while submerged.

The platypus was once commonly known as a "duckbill". However its bill is rubbery and flexible, not hard like that of a duck.

Although the bill is quite tough (to enable the platypus to search for food amongst rocks and gravel) it is covered with skin.

Sometimes platypus are found with scars on their bill, suggesting that they have cut themselves on sharp objects in the water, such as broken glass and wire, or have been snagged on fishing hooks.

The front feet are equipped with large webs of skin that serve as highly effective paddles.

The webs are folded under the foot when the platypus is out of the water, making it easier for the animal to walk and use its strong claws for digging burrows.

Unfortunately, these highly specialised front feet are not adept at removing objects that become caught around the head or body. As a result, platypus can die after becoming ensnared in litter such as loops of nylon fishing line or plastic six-pack holders.

The hind legs of the platypus help to steer and stabilise the animal when it is swimming. The back feet end in a series of sharp, curved claws that are used like a comb to keep the animal's fur tidy and waterproof.

Both the front and back legs extend out horizontally from the body, providing a powerful swimming and digging action. However, it also forces the platypus to shuffle like a lizard when walking on land or crossing shallow areas of water, making them vulnerable to predators such as foxes and dogs.

The main function of the tail is to store up to 50% of the animal's body fat, providing an energy reserve if food is scarce.

Researchers rate the general physical condition of a platypus on a five-point scale by applying a "squeeze test" to the tail in order to assess the amount of fat stored there.

The tail is also used as a stabiliser when swimming, and being flat, it enables the platypus to dive quickly.

A female platypus can use her tail to collect leaves to make a nest in the breeding chamber, and it is used in burrowing.

She then also uses her curled up tail to hold eggs against her stomach during incubation.

The platypus tail is broad and paddle-like, quite unlike the tail of the Australian water-rat (the animal most likely to be confused with a platypus by observers) which is thin and also has a distinctive white tip.

Some early reports suggested that the platypus slapped the water with its tail to make warning sounds, similar in behaviour to beavers. In fact, there is no evidence for this, although when startled platypus will sometimes make a "splash-dive" - a rapid dive in which they seem to use the tail to thrust themselves downwards quickly.

This can produce quite a loud noise, and perhaps this was the origin of the tail-slapping myth.